1. Technical Field
The disclosure relates to a power module, and more particularly relates to a power module applied in a power converter.
2. Description of Related Art
High efficiency and high power density are always required for the power converter in the industry. High efficiency means reduction of power consumption, which is beneficial for energy conservation and emission reduction to protect the environment and reduce the use cost. High power density means small volume and light weight, which is beneficial for reduction of transportation cost and required space to reduce the construction cost; and the high power density also means the reduction of the usage amount of materials, which is further beneficial for energy conservation and emission reduction to protect the environment. Therefore, the pursuit of high efficiency and high power density is never stopped in the field of power.
There are different kinds of power converters for different applications. According to the converting types of power, the power converters may be divided into: a non-isolated AC/DC power converter, for example formed by an AC/DC power converter applied in a power factor correction (PFC) circuit; a non-isolated DC/DC power converter; an isolated DC/DC power converter; an isolated AC/DC power converter, for example formed by a PFC circuit and one or more DC/DC power converters; and other power converters such as DC/AC power converters, AC/AC power converters and the like. Since the characteristics of the power to be converted are different and the converting grade levels are also different, the power densities and efficiencies which can be easily realized are different among various converters. Taking the isolated AGOG power converter as an example, currently the general power density thereof in the industry is 15 w/inch3 and the efficiency thereof is about 92%, while the non-isolated AC/DC power converter, the isolated DC/DC power converter and the DC/AC power converter have higher efficiencies and power densities.
As described above, the high efficiency of the power converter means low power consumption. For example, when the efficiency is 90%, the power consumption for conversion is about 10% of the total input energy of the entire power converter, and for the power converter with the efficiency of 91%, the power consumption for conversion is reduced to 9% of the total input energy. In other words, each time when the efficiency of the power converter is increased by 1%, the power consumption thereof is reduced by 10% relative to the power converter with the efficiency of 90%, which is significant. Actually, the efficiency of the power converter is often increased in the grade level of 0.5%, and even 0.1%.
The power converter is generally provided with integrated power modules therein, and the devices in the power modules are connected through bonding wires, lead frames and the like, which causes a large number of parasitic inductances in the circuit. However, parasitic inductances in the circuit described above reduce the capability of two devices connected in series in the same bridge arm of the power module for helping clamp for each other, which generates voltage spikes or peaks when a turn-off operation is performed on the devices. This not only affects the reliability of the power module, but also causes various electromagnetic interferences. Even seriously, the greater the parasitic inductance is, the greater the voltage spike generated during the turn-off operation of the devices is, which finally results in the damage of the devices.